Fixing device having fixing nip formed by elastic roller and a back-up unit with cylindrical film and film guide including a plurality of ribs extending circumferentially along the inner periphery of the film

摘要

An image fixing device includes an elastic roller; a back-up unit forming a fixing nip with the roller therebetween, the back-up unit including a cylindrical film, a film guide, extending inside the film, for guiding the film, and an end portion guiding member including a guiding portion for guiding an inner surface of an end portion of the film. The film guide includes plural ribs contacting the film and arranged in a generatrix direction at positions upstream of the fixing nip with respect to a feeding direction of a sheet. The ribs have free end portions retracted more toward a downstream side with respect to the feeding direction of the recording material than the guiding portion of the end portion guiding member. An inside rib has a free end portion which is retracted more toward the downstream side than free end portions of the opposite end ribs.